I would say you should be reporting fortnightly so you don't get over or underpaid. That is what I did whilst on PPS. I currently don't report fortnightly even though I don't work set hours as such, but we have overestimated for this financial year in the hopes of getting a lump sum payment when the payments balance. I'd rather have less money in the short term than have to pay money back.

As far as "estimating for CCB" what do you mean by that? You just do one annual estimate or you report fortnightly, then everything is adjusted based on that. If you said you were working on average 30-40 hours a week, you'd be eligible for 60 hours of CCB per week.

Also, no, as you are partnered it won't matter who "receives" the FTB - me and DP split ours, 25% to him and 75% to me, the amount is the same irrelevant of who is the primary contact with Centrelink.